Acts weird when it rains!!

Ok here's what I'm having, recently especially when it rains, my blazer shifts kinda weird... not really shifting but it just feels, you know that feeling when the car shifts between gears, and it does it between 0 and 45 mph... feels like gas isn't kicking 
I've recenlty had a fuel pump installed, and couple days later my check engine light came on and it was my O2 sensor, I didn't change it and a week later the light went off!!
Any suggestions?

I would take a look at your ignition components (cap, rotor and wires) real close like.  Go out at night and mist the engine with water (spray bottle on a fine mist) with the engine running.  If you see sparks jumping to ground, then you have bad wires. 

When was the last time you did a tune up?

Back in octobor 07 I did everything rotor, cap, spark plugs and wires... changed my pcv valve and had a new fuel filter all done by december 07.
Tell you the truth, it feels a little bit the same before I replaced my wires, plugs, cap and rotor!!
but why??

What brand of parts did you use? 

I would pop the cap off and check for carbon trails on the pins inside as well as carbon buildup on the tip of the rotor.  Being humidity dependant points a big finger at the ignition system.

a mechanic suggested that my cap could be lose or untightend right... I checked it today and it seems pretty tight to me, wires are all tight in places!!

quote:

ORIGINAL: yazan84

Ok here's what I'm having, recently especially when it rains, my blazer shifts kinda weird... not really shifting but it just feels, you know that feeling when the car shifts between gears, and it does it between 0 and 45 mph... feels like gas isn't kicking 
I've recenlty had a fuel pump installed, and couple days later my check engine light came on and it was my O2 sensor, I didn't change it and a week later the light went off!!
Any suggestions?

Dude, I am having the exact same issues with my 01 Blazer, but the first time it was an intake valve I belive that they replaced. My serpantine belt also looked pretty warn down so that also got replaced. I do remember hitting one puddle on a rainy day on this ****ty road near my house but since that its in to the shop 2-3 times. Also one of the times it went there it was an O2 sensor they replaced. It just came back on last week then went off and it came back on today on my way home from work.

I also have the same issue. I think It's pretty common for these. I have a 96 4x4

quote:

ORIGINAL: yazan84

Back in octobor 07 I did everything rotor, cap, spark plugs and wires... changed my pcv valve and had a new fuel filter all done by december 07.
Tell you the truth, it feels a little bit the same before I replaced my wires, plugs, cap and rotor!!
but why??

 
It could mean that the new parts are defective.  I think that's what Kyle was getting at without saying it directly.  You see, this is always a possibility.  Just because you replaced something doesn't mean the new parts are good.  If I were you, I'd do the test Kyle mentioned to eliminate the wires as the problem.  If you don't find a bad wire, then your cap may be defective.  I don't know how to test this, but I'm sure somebody on here does. Hopefully they will answer.
 
A lot of people on here suggest only using AC Delco parts for ignition components.  Hope this helps.

One thing that has cropped up from time to time here is a plugged screen at the bottom of the distributor that may cause condensation under the cap.  If this is the case, then it really wouldn't matter what you are using for ignition components as your misfire could be happening inside the cap given the right conditions.  Something else to look into.

I would definitely put this screen on the 'usual suspects' list.

This thread is still going? WOW!
 
Replace the cap and rotor.
 
 
Tell ya what, next nice warm sunny day pop teh hood and spray the distributor cap with water from your garden hose while the engine is running, if she stumbles or dies, you found your problem.
 
I know someone will say it, so I'll post up the answer.
No you wont ruin your engine by running water over it. Not even from the pressure washer at the car wash, even if you drove 800 miles and you pulled in, popped the hood, and washed the engine down while hot. The engine is designed to handle water, the engine compartment is not sealed, water gets in there when its raining out. Drive through a puddle, it does spash UP. Not too mention water crossing while 4x4ing.
 
Teh only place you must not get water is in the intake. Water doesn't compress and you can fatally ruin your engine if you hydrolock it under load.